Add scdf-python-app. fix polyglot-python-task issue

dataflow-website/recipes/polyglot/scdf-python-app/Dockerfile

@@ -0,0 +1,9 @@
+FROM python:3.7.3-slim
+
+RUN pip install kafka-python
+RUN pip install flask
+
+ADD /util/* /util/
+ADD barista_app.py /
+ENTRYPOINT ["python","/barista_app.py"]
+CMD []